Power plants operating on geothermal fluid have been constructed in many countries throughout the world. The physical properties of extracted geothermal fluid, such as its temperature, pressure, flow rate and chemical capacity, are important factors that determine the design of the power plant. Power plants operating in geothermal fields where the temperature of the extracted geothermal fluid is under 200.degree. C. typically utilize an organic working fluid such as one of the Freons, n-pentane, isopentane, etc. In such plants, the extracted geothermal fluid is applied to a vaporizer containing organic fluid which is vaporized and supplied to a turbogenerator wherein expansion takes places generating electricity. The exhaust from the turbogenerator is applied to a condenser, typically air cooled, to produce a condensate that is returned to the vaporizer by a cycle pump to complete the organic fluid cycle. Typically, heat depleted geothermal fluid produced by the vaporization of the organic fluid is disposed of in a re-injection well that returns the heat depleted geothermal fluid to the ground.
In order to increase the thermodynamic efficiency of such a power plant, the heat depleted geothermal fluid produced by the vaporizer is first passed through a pre-heater producing further heat depleted geothermal fluid which is then disposed of by re-injection. While this approach is advantageous in that additional heat is extracted from the geothermal fluid thus increasing the generating capacity of the power plant, serious problems will arise when the mineral content of the extracted geothermal fluid exceeds certain limits. That is to say, some geothermal fluids have such a high concentration of minerals, such as silica, that incipient precipitation occurs within the pre-heater and/or in the piping that connects the pre-heater to the re-injection well, and/or, even in the well bore of the re-injection well itself. For obvious reasons, this is not acceptable. As a result, the use of pre-heaters is often precluded to the detriment of generating capacity.
It is therefore an object of the present invention to provide a new and improved geothermal power plant and method for using the same which provides a measure of control over incipient precipitation in the components of a power plant.